Resonant and nonresonant integrated third-order parametric down-conversion

Third-order parametric down-conversion describes a class of nonlinear processes in which a pump photon can be down-converted into triplets of photons. It has been identified as a source of nonclassical light, with capabilities beyond those offered by better-established processes such as spontaneous four-wave mixing. Here we discuss the implementation of third-order parameter down-conversion (TOPDC) in integrated photonic systems. We derive equations for the rates of TOPDC in a nonresonant (waveguide) and resonant (microring) platform, such that the scaling with experimental parameters can be plainly seen. We find that generally nonresonant platforms should be pursued for spontaneous TOPDC (SpTOPDC), whereas resonant platforms are more suitable for stimulated TOPDC (StTOPDC). We present a sample calculation for TOPDC rates in sample systems with conservative and accessible parameters. We find that StTOPDC should be observable with the current fabrication technology, and that with some progress in the design of TOPDC platforms, integrated SpTOPDC too could be demonstrated in the near term.